In pulp production processes, lignin is generated in large quantities as a by-product. It is often burned to generate heat and electricity. Despite the large-scale production of lignin, its utilization in high-value applications has remained a challenge. Recently, the production of lignin nanoparticles (LNP) and lignin polymers has gathered attention. The potential to use LNPs as reinforcement filler, UV absorbent, antioxidant, and drug carrier has been reported, while lignin polymers might be suitable for the production of composites, hydrogels, flocculants, and coagulants. This review paper provides insights into the production and application of LNP and lignin polymers. In addition, the challenges associated with the characterization and use of these products are comprehensively reviewed.